Chemotherapy has been a major advance in cancer therapy. It is not used alone as an initial treatment of breast cancer, but is often used with mastectomy or radiation or both. Adjuvant chemotherapy is commonly used in patients whose lymph nodes show signs of cancer, indicating a high risk of distant spread. Treatment, usually administered in brief courses given every three or four weeks, may continue for a year or longer. The length of therapy is not necessarily related to the seriousness of the disease.
Adjuvant chemotherapy for breast cancer usually involves a combination of drugs, sometimes three or four, given intravenously. Among the types of drugs prescribed are alkylating agents, such as L-phenylalanine mustard (L-PAM or melphalan, with the brand name of Alkeran) and cyclophosphamide (Cytoxan). These agents work by interfering with the division process of cancer cells. Other chemotherapy agents include an-timetabolites, such as 5-fluorouracil (5-Fu) and methotrexate, which interfere with the formation of metabolic substances that are essential to production of DNA in cells.
Some antibiotics, such as doxorubicin (Adriamycin), are also used, because they interfere with the duplication of DNA needed for cell division. Finally there are mitotic inhibitors, such as vinblastine sulfate (Velban) and vincristine sulfate (Oncovin), derivatives of the periwinkle plant, which interfere with the separation of the cell’s essential genetic information into two distinct daughter cells.
The use of adjuvant chemotherapy to treat breast cancer started in 1958 in a study conducted as part of the National Surgical Adjuvant Breast Project. Patients were given low doses of an anticancer drug for two days following surgery. Although the regimen was much more restricted than what is now proposed, premenopausal women with four or more positive lymph nodes who took the drug experienced improvement in both five- and ten-year survival. A recent consensus panel convened by the National Cancer Institute found that adjuvant chemotherapy is of most benefit to younger premenopausal women whose cancer had spread to the lymph nodes. No added benefit has as yet been proved for women with localized cancer and no lymph node involvement.
While chemotherapy does increase the effectiveness of surgery or radiation therapy, it is not without side effects, although most are reversible. Nausea, loss of appetite, temporary hair loss, temporary bone marrow depression (which increases susceptibility to infection and bleeding), anemia and fatigue are common. The drugs can also interfere with menstrual function and produce symptoms of menopause. Adjustments in dosage and method of administration can alleviate many of these side effects. Others, such as nausea, can be prevented or treated. Hair loss, commonly seen with the use of such drugs as doxorubicin (Adriamycin), can be prevented in up to half of all patients with the use of a scalp-cooling device.
Different types of breast cancers respond differently to chemotherapy. Responses of patients to the drugs also vary. For this reason drug therapies must be evaluated periodically to be sure that the medication is effective, or continues to be effective.